Addiction and physical dependence can follow the use of all forms of tobacco (e.g., cigarettes, chewing tobacco, snuff, pipes, cigars). The development of addiction and physical dependence and the severity of potential withdrawal symptoms depends on how fast the nicotine is absorbed into the body and how much nicotine is in the product. Nicotine that is smoked is absorbed faster than nicotine that is chewed. Both of these routes of administration are faster than absorption through the skin.

Nicotine is a highly addictive substance with immediate withdrawal symptoms. Many people who use nicotine do so to avoid or relieve these symptoms, which may appear in as little as an hour after their last use. Of all the nicotine products available, cigarettes cause the most rapid onset of nicotine effects. This tends to lead to heavier use and makes smoking more difficult to quit. In addition, when patients who smoke cigarettes attempt to quit smoking, their symptoms of withdrawal are generally more severe than those of patients who use other nicotine products.

Smoking or the use of other nicotine products leaves many noticeable signs in patients. Signs of nicotine use may include:

• Tobacco odor on clothes, breath and hair
• Chronic cough
• Excessive skin wrinkling
• Tobacco stains on the fingers and teeth

Patients who stop or attempt to stop using nicotine typically experience a period of withdrawal. The onset of withdrawal symptoms usually begins within a few hours of quitting, and intensifies between the first and fourth day after the last use of nicotine. Symptoms usually lessen after three to four weeks.

Craving nicotine is often the most apparent symptom of withdrawal. Patients who stop using nicotine may also experience weight gain. This increase in weight, which may stem from an increased appetite or patients' efforts to distract themselves from smoking by eating, tends to be around four to seven pounds (about two to three kilograms) over the first year after quitting. Other symptoms of nicotine withdrawal may include:

• Depression
• Irritability, impatience, frustration or anger
• Anxiety
• Insomnia
• Difficulty concentrating and reduced vigilance
• Decreased heart rate
• Cough